This invention relates to an inter-connection between a printed circuit board within a device and equipment external thereto, and in particular to an arrangement for directly coupling a circuit board conductor to a connector to facilitate inter-connection.
Transferring signals to and from printed circuit boards within an electronic device invariably involves printed circuit board connectors which couple signals to ribbon or wire conductors, coaxial cable etc. The ribbon, wire or coaxial conductors in turn couple the signals from the printed circuit board connector to and from a connection panel which provides an input output capability via conductors coupling to external plant equipment. It can be appreciated that the exemplary signal coupling from a printed circuit board to an I/O connector represents a significant manufacturing cost in terms of both materials and labor. In addition, electronic equipment functioning with high frequency signals, for example in a range from 10 mega Hertz to beyond 1 giga Hertz, can suffer impaired performance. For example, if signal and signal return conductor impedance variations or discontinuities exist at each conductor junction, degraded signal propagation can result. Such impedance discontinuities, also known as return loss, will cause unwanted and undesirable signal reflections which degrade the wanted transmission signal by adding and or subtracting various components of the transmission signal and limiting the maximum interconnection length or signal detection threshold etc.
It is known to provide a direct connective arrangement between a printed circuit board conductor and a connector mounted to the printed circuit board such that when inserted within a module frame or chassis the on-board connector protrudes beyond the module frame, or chassis to provide an I/O connection at a panel. Such an arrangement provides lowered manufacturing and material costs. However, with this arrangement, any subsequent maintenance requires that the user have physical access to the rear connector panel in order to disconnect cabling prior to module removal. Furthermore, any requirement for cable or harness disconnection increases the likelihood of erroneous or wanted signal interruption.
In a further arrangement printed circuit board, PCB, edge conductors are located at a module edge such that when inserted into a module frame the printed edge conductors extend or protrude into and mate with an end portion, or mounting throat of a bulkhead or chassis mounted BNC connector. The connector initials BNC are derived from the bayonet fixing method and the inventor""s name Neil Concelman. This connective method offers the advantages of reduced parts count and reduced manufacturing and assembly costs. In addition this connective arrangement can provide a better impedance match between the BNC connector and the PCB conductor, for example, if configured as a micro strip line conductor.
However, maintenance considerations for the repair of an electronic module with such a connective arrangement must facilitate module withdrawal, preferably from the front of the electronic device without any requirement to disconnect cabling at the chassis rear. Clearly, to facilitate multiple withdrawals and insertions of the PCB connector from the BNC mounting throat requires excellent contact performance for both the signal and signal return or ground connections. To provide a return signal connection spring ground clips have been employed attached to the BNC body, as shown in FIGS. 1A and 1B. However this BNC to PCB signal grounding arrangement proved unreliable during multiple insertion and removal cycles. Frequently collisions occurred between the PCB edge and the spring grounding clips causing bending or mechanical deformation. At best the return loss of the connective junction is compromised but more frequently the mechanical damage is such to prevent module insertion and occasionally resulting in signal conductor short circuits. Such spring clip damage is not easily repairable, and requires that the equipment chassis is un-cabled and mechanically disassembled to allow the repair of the hard mounted grounding clips attached to the BNC connectors at chassis rear panel.
In an advantageous arrangement the signal grounding problems discusses previously are obviated by a circuit board arrangement which facilitates a direct connection to a chassis mounted connector. The arrangement comprises a printed circuit board with a first signal conductor terminating at an edge of the printed circuit board. A second signal conductor is disposed adjacent to the first signal conductor and terminates at the edge. A conductive metallic spring clip has a relieved area and is formed to fit over the edge of said printed circuit board. The conductive metallic spring clip is positioned on the edge of the printed circuit board such that the relieved area straddles the first signal conductor and the conductive metallic spring clip grips the second signal conductor for coupling the second signal conductor to the chassis mounted connector.
In another inventive aspect the conductive metallic spring clip is compressed during insertion into a mounting throat of the chassis mounted connector and advantageously provides a wiping action between the PCB conductors and the mating connector surfaces.
In a further inventive aspect the conductive metallic spring clip is advantageous attached to the PCB by various methods that allow the clip to be slid over the module edge connector and, for example, detent in aligned holes in a PCB signal ground conductor. Thus the inventive conductive metallic spring clip is substantially non-detachably retained on the PCB module to facilitate multiple module insertion and withdrawal cycles.
In yet a further inventive aspect the conductive metallic spring clip can accommodate a degree of movement or misalignment as a consequence of PCB warpage or lack of manual dexterity during module insertion.